The present invention relates to a monitoring device and more particularly to a device which senses flaws in yarn being manufactured in an open end rotor spinning machine as a result of changes in centrifugal force being applied to the yarn.
For the purposes of economical production in the yarn processing textile industry, yarn which is turned out by spinning machines is usually wound on pirns. This requires that the yarn be rewound on spool machines for making up large format spools. Normally, the yarn is cleaned during this rewinding process. The thread is cleaned in this process by the removal of thick bulky points, either by means of slit cleaning or by means of electronic thread cleaners which, for example, are functionally connected to a thread cutting device (German Patent Laid Open to Inspection No. 2,132,137). Associated with the slit cleaning device is a thread sensor that triggers the stoppage of the spool responsive to the breaking of the thread.
The yarns which are spun according to the open end spinning method are already wound up into cross spools at their spinning point and a respooling merely for the purpose of threading cleaning is uneconomical. It, therefore, has already been proposed to transfer the arrangement of slit cleaner and thread sensor, which are known from spool cleaning machines, to an open end spinning device (German Patent Published for Opposition, No. 1,814,033).
Slit cleaners, however, influence the thread quality unfavorably. The thread is roughed up by the edges of the cleaner and thus gets a rather hairy appearance. Besides, there is a danger that the thick places, which are only a little larger than the width of the slit, will pass through the cleaner without causing the thread to break off. Preference is, therefore, given to the use of electronic yarn cleaners which work on a capacitor or optical basis. The measurement value detectors of this type of device are expensive. They are furthermore exposed to environmental factors and operating conditions which impair their response sensitivity. Another disadvantage exists in the fact that these systems are influenced by the passage speed of the thread so that it cannot fall below a certain speed.